The Phenotyping Core (Core B) is designed to evaluate the functional properties of muscles, joints, and whole animals in animal models created by the various Center investigators or directly in human muscle. The Phenotyping Core will interface with the High Throughput Cell Sorting Core and the Imaging Core by helping Center investigators identify the appropriate functional evaluation of muscle, with special consideration of the specific manipulation created by the Center investigator. The quantitative functional evaluation conducted by the Phenotyping Core will often be combined with structural data obtained from the Imaging Core thereby providing possible mechanistic explanations for any functional effects that are found. Thus, the Phenotyping Core will provide accessibility to sophisticated physiological and biomechanical testing capabilities to all Center investigators. The Specific Aims of the Phenotyping Core are: 1) To provide training and technical assistance in skeletal muscle identification, dissection and mounting for isolated contractile and metabolic studies of isolated muscles. 2) To provide training and technical assistance in developing specialized jigs and interfaces to measure joint or muscle torque, or to conduct whole animal funcfional measurements. 3) To provide technical assistance with snap-freezing and routine histological processing of skeletal muscle including hematoxylin and eosin, immunohistochemistry, quantitative morphometry, and qualitafive morphology. 4) To provide training and technical assistance in measuring various aspects of metabolism either in vivo of ex vivo in muscle.